Sunday, September 22, 2013

Now that autumn is here and a seasonal quietness descends, I go to the window box several times every day to see if I can find any invertebrates. This has proved quite successful. Today, for example, I found a walnut orb-web spider, Nuctenea umbratica.

These hide in suitable crevices by day (this one was tucked neatly behind a stipule on one of the sallow wands) and spin their web as dusk falls. It is one of the few British spiders capable of biting humans, but if it does it only causes a little mild irritation.

Wednesday, September 11, 2013

The two pebble prominent larvae I brought indoors from the window box sallows the other day are now nearly fully grown and resemble one another rather little. One is much larger and I would estimate about two and a half times the size of the other.

It could be that the smaller, paler one (below) will be a male, but I am not sure at which stage sexual differentiation in moths and other invertebrates occurs. The size of the lower one, by the way, is overestimated by these photos and remember, the head is on the right

Wednesday, September 04, 2013

I have discovered a third pebble prominent, Notodonta ziczac, caterpillar feeding on one of the coppiced sallows in the window box.

The head is on the left hand side and the tail on the right is normally raised (or lowered in this case) perhaps to entice predators to attack the wrong end, or not to attack at all. The caterpillar is still quite small so, if it survives in the window box jungle, there should be more pictures.

The specific name ziczac is said to derive from the German zick-zack (meaning 'zigzag'). It was Latinised to 'ziczac' by Linnaeus when he named the species and is said to refer to the unusual shape of the larva.

Monday, September 02, 2013

In the last few weeks I have found the caterpillars of many different species of moth on the sallow coppice in the window box. The top one in the pictures below is a baby pebble prominent, Notodonta ziczac. Interestingly it seems to have two 'horns' on either side of the head (on the left) which I think are not present in later instars.

The second picture below is of what I think is a caterpillar of one of the thorn moths.

While these caterpillars seem to resemble twigs, they are also very much like bird droppings, especially the pebble prominents which tend to site themselves at the apex of the leaf they are eating. Inevitably this is said be an imitation that makes them difficult to see, But if I can find them easily enough, why does it fool the sharp-eyed birds for whom they are a tasty morsel?

There are also two different green caterpillars on the sallow. I found the top one when it was quite small and it is growing rapidly. The other is, I think, not going to grow to any great size.

Finally, there is a small caterpillar hiding (not very well) in a kind of silk awning it has sung across one of the larger leaves.

I keep examples of these caterpillars in plastic boxes with supplies of leaves and, usually, they pupate and I have to wait until the moths emerge when they can be photographed and released.